Hey Bruce, welcome to the club!
I got my coach in March this year - it had been stored indoors for 10 years in a school bus depot in Belleville Ontario. I took delivery of it in Scotch Creek BC and drove it down to Vancouver Island. The owner's brother had driven it from Belleville to BC the previous summer - uneventful, except for replacing the water pump somewhere in the prairies.
At first, because I was buying the coach sight unseen and thinking everything was original, I started looking for some 16.5 tires as I didn't fancy driving the 400 miles down through the canyon on old rubber.
Eventually I got a friend (friend now, but at that time just a contact I found through the blacklist) to go check the storage yard in Scotch Creek and was relieved to find the steel wheels were replacements. She was fitted with 16's not 16.5's.
I ordered 7 new Kumho's from blackcircles.ca (based in Quebec) and had them delivered to a tire installer in Chase BC. I think the total cost for 7 was somewhere around C$1300 incl tax, delivered.
The blackcircles website doesn't show 16.5 as an option, but they can of course supply any tire. I know they have access to Firestones and any oher brand you fancy - give them a call, I found them to be extremely helpful on the phone.
Matt has suggested looking around for some 16" steel rims and if you do that, many more tire options come to light. I'd love a set of alloys from JimK in California, but with US$ and shipping, well, y'know the rest. If cost is no concern, go for it. Personally I like a deal, so my steel wheels and a $100 set of chrome plastic covers from eBay suit me fine.
I've been told I'm one of the lucky ones. I did spend about 3 months getting the coach systems up to snuff and doing all the long overdue maintenance/repairs, but when July rolled around I was able to hit the road and used her all through the summer. At my advanced years

I can't take on projects that last too too long ...(although I did buy another boat last week ---eeek!)
cheers
Larry